This disclosure relates generally to an aircraft auxiliary system and, more particularly, to influencing back pressure at an exhaust of the aircraft auxiliary system.
Auxiliary systems are used in many aircraft. One example auxiliary system, an auxiliary power unit (APU), mounts to structural members within a tail cone of the aircraft. Aircraft skin secured to the structural members encloses the APU within a cavity. Other auxiliary systems are located in other areas of the aircraft.
An inlet duct extends from an outer surface of the aircraft skin to the auxiliary system. Fluid communicates to the auxiliary system through the inlet duct. A door may selectively cover an opening to the inlet duct to restrict flow to the auxiliary system. An exhaust duct communicates exhausted fluid from the auxiliary system.
As known, back pressure is a function of the air flowing over outwardly facing surfaces of the aircraft skin interacting with the exhausted fluid. If the back pressure is relatively high, the efficiency of the auxiliary system may undesirably decrease. For example, relatively high back pressure levels can reduce flow through the APU, which inhibits the ability of the APU to cool an aircraft cabin.